Some reasons for nonsaturation of reverse current in junction diodes

The saturation of reverse current for reverse voltages more than a few tenths of a volt, which is predicted for semiconductor junctions by the simple theory, actually never occurs. Effects such as surface conduction and generation of minority carriers in the space-charge region have been used to explain the failure of the current to saturate. The present discussion considers some other possibilities. For nonplanar junctions, increase in the effective junction area with increasing reverse bias may be important. For any junction, increasing bias may move the effective junction surface to places where the semiconductor has, either actually or effectively, different properties. Some examples of these possibilities, chosen to be as closely related to practical devices as possible, are given.